The present invention relates to a process for producing porous materials of carbon and, more particularly, to a process permitting manufacture of porous materials having a large quantity of continuous pores, i.e., containing most of pores being continuous.
Heretofore, there is a process for producing porous materials of carbon having been produced by employing as a binder ground hollow materials of carbonaceous compound and calcining the material (disclosed in Japanese Patent Application Laid-open No. 19,999/1974). However, the porous materials produced by this process has such disadvantages that most of their pores are independent and a small quantity of pores are continuous and the porous materials accordingly have of lack of permeability. There is another process for obtaining porous materials of carbon having continuous pores, by impregnating reticulated polyurethane having continuous pores, from which thin partition walls of foamable polyurethane are removed with tetrahydrofuran solution of phenol resin, calcining the impregnated porous polyurethane permitting the reticulated polyurethane skeleton of base materials to become the skeleton of the carbide (disclosed in U.S. Pat. No. 3,922,334). According to this process, there are drawbacks that it is necessary to pay much attention to remove the excessive resin on the surface of the polyurethane after impregnating with the resin. In addition, the foamable polyurethane might be dissolved according to the selection of a solvent, and the foamable materials might sometimes be broken at the heating time, and this trend becomes remarkable as the polyurethane becomes softer. In order to obviate these drawbacks, there is another process for producing porous materials of carbon by impregnating in advance the foamable polyurethane with liquid epoxy resin or aqueous polyvinyl alcohol solution before impregnating with the resin (disclosed in Japanese Patent Application Laid-open No. 70,207/1976). However, the steps of this process are complicated. Since the foamable polyurethane originally has independent pores, it is necessary to obtain a reticulated structure having continuous pores to remove in advance the partition membranes of the pores or to similarly impregnate with the resin. In the latter case, there is a process for obtaining porous materials of carbon having continuous pores by introducing combustible gas into a foamable thermosetting resin produced by reacting polyisocyanate with phenol resin, furan resin or a mixture thereof with its pretreated substance, igniting the combustible gas to break the partition membrane and then carbonizing and calcining the materials (disclosed in Japanese Patent Application Laid-open No. 125,289/1978). However, the steps of this process are very complicated, and it is further difficult in this process to control the diameter of the pores. There is disclosed as a process for manufacturing porous materials of carbon having large continuous porosity including even diameter distribution of pores a process for producing porous materials of carbon formed at least partly of glassy carbon by mixing polyvinyl alcohol, phenol resin, hardening agent, starch and aqueous soluble salts, crosslinking and molding the mixture, solidifying the mixture, then extracting aqueous soluble substance by water to calcine phenol polyvinyl acetal synthetic resin imparted with continuous pores thereto, and producing porous materials of carbon formed at least partly of glassy carbon (disclosed in Japanese Patent Application Laid-open No. 51,109/1982). Further, there is disclosed another process for producing porous materials of carbon having continuous pores formed at least part of glassy carbon by impregnating porous materials of polyvinyl acetal having continuous pores containing inorganic materials or organic material to be carbonized with phenol or furan resin to be transformed into glassy carbon and then calcining the impregnated material (disclosed in Japanese Patent Application Laid-open No. 51,110/1982). However, the process should employ complicated steps such as premixing starch or aqueous soluble substance such as aqueous soluble salts with the polyvinyl acetal similarly to the previous process before preparing continuous pores, crosslinking and molding the substance, and then extracting the substance. Further, this process has drawbacks that the complete removal of the starch or aqueous soluble salts from the polyvinyl acetal molding is extremely difficult.